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Post by navajoflyer on Sept 17, 2018 15:45:21 GMT -9
Been chasing a strange oil temp indication problem for the last couple months. The right oil temp goes full scale occasionally, but if you actuate the cowl flap the indication goes back to normal sometimes for hours sometimes for minutes. We’ve swapped indicators, and temp probes no help. We’ve also bypassed the wing connector, checked al the power and ground nothing has helped. Any ideas would be appreciated.
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Post by ronnie27478 on Sept 18, 2018 6:00:04 GMT -9
Here is a thought you might consider. The oil temperature probe is a thermocouple which generates a millivolt level voltage that is dependent on temperature. The oil temperature gauge measures this voltage or resulting current and displays it as temperature. To get the gauge to read full scale, a higher than normal voltage would have to be impressed on the "hot" wire, E71FB (outside the wing root connector) or E70EF (inside the wing root connector) See Figure 11-100 or Figure 11-101 in the service manual, depending on your serial number. I would check for broken / worn / chaffed insulation on these wires. Perhaps there is an intermittent connection to either the cowl flap motor circuit or the cowl flap indicator circuit in the wire bundle on either side of the wing root connector. Or perhaps there is an intermittent connection to another energized wire in the bundle and moving the cowl flaps moves the wire bundle a bit and opens the connection for a while. Wires E43FB & E2EF are the ground side of the probe which connects to the ground of the gauge, which is common with the cylinder head temperature gauge ground and air frame ground. If there was an issue in these wires, I would suspect the gauge would peg to the low side and there would also be an abnormal cylinder head temperature indication. Although I guess an intermittent open circuit in the ground side wires could allow an induced noise voltage to drive the gauge to higher than normal reading. Just an idea. Otherwise, I don't see any correlation between cowl flap operation and oil temperature indication. Ronnie  |
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Post by navajoflyer on Sept 18, 2018 17:39:37 GMT -9
Thanks
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Post by ronnie27478 on Nov 12, 2018 12:53:26 GMT -9
Did you ever find the root of the problem?
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Post by navajoflyer on Nov 24, 2018 15:32:31 GMT -9
Never solved the problem, it's been ok now for almost 2 months. I hate when this happens, I'm sure it will be back at some incredibly inconvenient time.
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Post by armaiabuw on May 27, 2019 5:47:56 GMT -9
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Post by oenojadabit on May 27, 2019 8:06:21 GMT -9
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Post by n619pr on Jul 3, 2020 9:17:39 GMT -9
I have the left oil temp fluctuating problem also, but it registers fine on the G4 so this will wait the next annual.
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